System Sensor FAAST Comprehensive - Manual (Page 31)

pipe Bends
Never bend pipes, unless absolutely necessary. Use elbows, tees or other fit-
tings to change the direction of the pipe.
If bending is necessary, determine how much bending the pipe can tolerate
before beginning the process. Always use bending springs and pipe benders.
Never heat the pipe or bend it around sharp objects. If a pipe is kinked while
bending, replace it with a new section of pipe. Conform to all local codes and
regulations for bending of pipes.
Drilling Sample holes
Each hole in the sampling pipe represents a smoke detection location. Hole
placement and size are determined using the PipeIQ software. Sample holes
should be drilled after the pipe network has been installed. To prevent sam-
pling holes from being blocked by dust and dirt, place the holes on the bottom
side of the sampling pipes, not on the top of the pipe. This ensures that any
falling debris does not clog the sampling holes. This hole positioning should
also be followed for voids in the ceiling or floor.
The following guidelines should be followed when drilling the sample holes
in the pipe network.
• Holes must be drilled perpendicular (90 degrees) to the pipe. If the drill
is not held perpendicular, the hole is not round and may affect air flow.
• Sampling holes must be drilled exactly at the positions marked on the
pipe with the exact size determined by the PipeIQ software.
• Holes must not be drilled through both sides of the pipe.
• Holes should be drilled with a slow speed drill with a sharp drill bit. This
minimizes dust and burrs entering the pipe network.
It is always good practice to blow compressed air through the pipe after drill-
ing to clear any debris before final connection to the FAAST detector. Alter-
nately, a shop vacuum can be used to remove debris from the pipe network.
Remove the end cap and use the vacuum to draw the debris through the end
of the pipe near the FAAST system connection.
DiluTion in ASpirATion SYSTemS
Air from an aspiration system is drawn in from several sampling points along
the pipe network. Because of this, air from a single point in the system is
diluted by the combination of air from the entire system. This affects the con-
centration of smoke particles in the air that reaches the detector. The dilu-
tion effect must be accounted for when designing the overall FAAST system.
PipeIQ automatically calculates the primary factors contributing to the effects
of dilution on the system.
A general guideline for the effect of dilution on the pipe network is given in
the following example. A smoke source of 2% obscuration/ft is introduced at
the far end of a pipe having 10 sampling holes. No other smoke is entering any
of the other sampling holes. As the smoke passes each hole, the smoke filled
air is added to with clean air. When the sample reaches the detector it is now
at 0.2% obscuration/ft. or 1/10th of its starting density. Therefore if the first
alarm threshold is set at 0.2% obs/ft., the smoke outside the hole must exceed
2%/ft. to sound the alarm.
The longer the pipe and the greater the number of sampling holes, the more
susceptible the system will be to dilution. It is better to operate on the conser-
vative side of the situation due to the variable influences on the system. In ac-
tuality, the calculation of dilution is not as straightforward as above and more
factors are involved. Each system will have different characteristics, meaning
precise calculation is complicated. Issues that will affect the dilution rate in-
clude size, location and number of holes, tees, elbows and joints, diameter of
the pipe itself, as well as, outside elements such as air temperature, pressure
and humidity.
SS-400-007 32 E56-3621-003
The Pipe System